Digital camera with reduced image buffer memory and minimal processing for recycling through a service center

Abstract

A digital camera system in which capture, processing and storage functions are partitioned differently than in existing systems. A hand-held digital camera is used with a workstation that may exist in a commercial image processing service center. A minimal amount of image data processing is performed in the digital camera, thereby allowing significant digital camera cost reductions due to lower memory requirements, lower processing requirements, and lower power requirements. Real-time single pass image compression techniques are employed within this digital camera to permit rapid gathering and storage of raw or minimally processed image data. The workstation to which the image data are transferred performs the image processing normally done within existing cameras. This processing takes advantage of the increased computational power that is possible to have in such a workstation, compared to that of a small camera, and the increased time over which such processing may be performed.

Description

FIELD OF THE INVENTION[0001]This invention relates generally to hand-held digital cameras and methods of using them, and, more specifically, to such a camera having a simplified electronic system and minimal image processing that is instead performed by a workstation to which data of images captured by the camera are transferred.BACKGROUND[0002]Electronic cameras image scenes onto a two-dimensional sensor such as a charge-coupled-device (CCD), a complementary metal-on-silicon (CMOS) device or other type of light sensor. These devices include a large number of photo-detectors (typically two, three, four or more million) arranged across a small two dimensional surface that individually generate a signal proportional to the intensity of light or other optical radiation (including infrared and ultra-violet regions of the spectrum adjacent the visible light wavelengths) striking the element. These elements, forming pixels of an image, are typically scanned in a raster pattern to generate...

AI Technical Summary

Benefits of technology

[0008]According to one principal aspect of the present invention, the process of converting the digital image from the sensor in the camera to the format that is ultimately delivered to the end user is partitioned between the camera processor and a data processing workstation, such as a workstation in a commercial service center, in a way that minimizes the amount and complexity of processing done in the camera. It does this by transferring a majority or all of the image processing traditionally performed within digital cameras to the workstation. Raw or nearly raw digital data of the signal output of the image sensor, or a compressed version of it, are acquired and stored within the camera and then transferred to the workstation. In addition to this image data, various support data may be stored along with the image data within the camera in order to facilitate processing by the workstation to which the data are transferred. Such support data can be derived from a prior camera calibration, from an additional sensor within the camera, from a second image taken under different conditions or obtained from an analysis within the camera of the image data itself. In addition to reducing the complexity and cost of the camera in this way, the workstation can also provide more powerful processing that has been considered to be too costly, too physically large, too time consuming or too power consuming to be included in a digital camera. This results in pictures with significantly improved quality being obtained by the end-user with a digital camera of reduced complexity and cost.

[0009]According to another principal aspect of the present invention, image digital data is compressed within the camera in real-time and in a single-pass through the acquired sensor data in a manner that also reduces the complexity and cost of the digital camera. The method of compression implemented in the camera's processor is not constrained by the convention of compliance with a standard, such as the Joint Photographic Experts Group (JPEG) standard, since the workstation can be complementarily configured to receive the compressed data from such a camera, yet the advantages of JPEG compression can still be realized. The entire digital image frame received from the sensor need not be stored in an image frame buffer memory, prior to compression, as is commonly done in most digital cameras. Instead, only a small portion at a time of the digitized data of an image frame needs to be stored prior to compression. By this means, a separate digital memory integrated circuit chip normally dedicated to storage of the image prior to compression can usually be eliminated from the camera, thus reducing its complexity, eliminating operational constraints imposed by the separate memory and reducing the manufacturing cost. If temporary storage of the entire image frame is required at all, it is only of the reduced size compressed picture frame, not the much larger amount of data of the image frame prior to its compression. Thus, the total need for temporary image data storage can be reduced considerably. At the workstation at the service center or otherwise, the compressed pictures are retrieved from the non-volatile memory in the digital camera used to store the captured image work product, and decompressed. After decompression, the workstation completes the processing of the image data to optimize picture quality and correct for imperfections in the camera, all the processing that commercial digital cameras now do, as outlined above, and more. The decompressed and processed image data is then put into a form for utilization by a color printer, for writing onto a CD or DVD, or some other end use. When preparing the data into standard format files for writing onto a CD, the workstation processes the pictures by compressing the data into a standard, such as the JPEG format standard.

[0010]According to a further aspect of the present invention, a digital camera may be configured to take at least two pictures of the same scene in rapid succession, and then process the data of the two images to produce a single image of the common object scene that has a quality that is better than the quality of either of the acquired images, that corrects for defects in the acquired images and / or which compensates for limitations of camera. For example, the effect on the image of defective pixels of the image sensor can be eliminated when the image on the camera sensor is shifted by at least one pixel between the two exposures, an extremely small shift that certainly occurs between two successive exposures with a hand-held camera. Data of portions of one image containing the effects of defective sensor pixels are replaced by data of the same portions of the object scene acquired by the other image, which, because of the camera motion between pictures, are acquired by different sensor pixels. The effects of fixed pattern noise of the sensor, the camera optics and the electronic system can corrected in the same way. An advantage of making these corrections in this way is that they are dynamic; that is, changes in the sensor or optics over time are corrected automatically without having to separately measure them. Another example is increasing the light sensitive dynamic range of the camera sensor by acquiring two or more images of the same object scene under different exposure conditions and then combining them. This allows restoration of details of portions of an acquired image that are either predominately dark or bright because of sensor pixels being saturated. Further, image details that are blurred by a camera moving during exposure may be sharpened by making two such exposures in rapid succession and then processing the data of both images with an inverse smearing algorithm.

Problems solved by technology

In addition to reducing the complexity and cost of the camera in this way, the workstation can also provide more powerful processing that has been considered to be too costly, too physically large, too time consuming or too power consuming to be included in a digital camera.

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